Actually it is true. The tips on the link you posted are just tips but also won't help you much if you had a non weebly website. Much like if you wanted chicken for dinner, I could give you a tip and say "season with salt". Won't guarantee it will be tasty!
To run SEO effectively for example we have 77 line items/tasks per month. If one task is posting 9 pieces of written content on 10 social sharing sites, that is one line item/task not 9.
With weebly you can't even build a landing page on it because it has no data base, you first need to acquire a separate third party domain. Which also means you cannot run a ppc campaign directly off weebly.
This question comes up a lot and there is no weebly website you can reference that ranks in organic search UNLESS it is massively popular with several million monthly viewers which is highly unlikely in your case.
Doing the 6 odd tips they suggest sounds great but not effective. To run SEO you first need to know what keywords to rank for. To do that you need to research several hundred to thousand webpages to see how those keywords perform, what grade they are, what the competition level is and then make a decision on which ones to go for.
Why? Well how do you know if the competition level for those keywords is say 180%? That means you have no chance in this lifetime at all for ranking for that/those keywords as an average website.
How do you know if there is zero search volume on those keywords? Which means no one on earth is search for them.
How do you know how to grade such keywords? Did you know keywords/phrases are graded?
There are a lot of factors involved in SEO and just because weebly offer you 6 odd tips does not mean if you ran those 6 tips 200 times daily you will see any results.
What we have found is the number 1 reason prospects/customers past SEO efforts have failed prior to talking to us is because the foundation was all wrong, followed by zero research. Why do you think some companies offer you SEO ranking in 24hours? Because NO ONE IN THE WORLD SEARCHES FOR THOSE KEYWORDS!!!
Once your research is complete you then have to choose you're primary and secondary keywords and allocate them to the relevant product/service pages with a maximum of 3 keywords per product/service page, then you group your keywords, ensure the url architecture is in order, map them out to target URL's, manual site crawlability and hidden links check.
Then you go on to set up your accounts where you are going to publish content. Like your 10 major business directories set up, top 5 press release accounts set up, Google + authorship account (to ensure your content has your stamp on it and if copied by whomever YOU alone take the credit; allllllllll the way down to reporting and analytics brings you to our 77th monthly task.
If you cannot do this, then you cannot do SEO and if you doubt it, I'd challenge you to show me 1 single weebly site on earth that ranks for major keywords that is not massively popular.
An example of a massively popular App is Tinder. I can prove this by the way if you are still in doubt.